Graphical Representation of Wave PDF

**GRAPHICAL REPRESENTATION OF WAVE** **Displacement-Distance Graph** A displacement-distance graph describes the displacement of all particles at a particular instant of time. Note that displacement of particle is plotted on y-axis and distance moved by the wave is on x-axis. The arrows shown on...

**GRAPHICAL REPRESENTATION OF WAVE** **Displacement-Distance Graph** A displacement-distance graph describes the displacement of all particles at a particular instant of time. Note that displacement of particle is plotted on y-axis and distance moved by the wave is on x-axis. The arrows shown on the graph indicate the direction of the displacement of vibrating particle. According to the graph the amplitude is 0.6 cm and wavelength is 5 m respectively. Displacement-Time Graph A displacement-time graph describes the displacement of particle of a certain position as a function of time taken to travel by a wave. Note that displacement of particle is on Y axis and time interval is on X axis. Unit Displacement (cm) According to the graph, the amplitude and the period of the wave are 0.6 cm and 0.5 s the frequency of the wave is 2 Hz. **7.5 REFLECTION, REFRACTION AND DIFFRACTION OF WAVE** Wave can undergo reflection, refraction and diffraction. These phenomena are usually studied by means of water wave in a ripple tank. Ripple Tank: The ripple tank is a convenient piece of apparatus for demonstrating the properties of waves. Wavefront: The surface that joins all the points of same phase is called wavefront. **Reflection** When a series of wave strike an obstacle, they are turned back. This turning back of waves is called reflection of waves. When waves strike a straight barrier, the waves are reflected from the barrier. The angle of incidence is equal to the angle of reflection as shown in Figure 7.12. The wavelength and velocity of the wave remain constant in reflection of wave. wavefronts approach **Refraction** Figure 7.15 Reflection of radio waves The speed of water waves depends on the depth of water. It decreases when the depth of water becomes less deep. By the ripple tank experiment, when water waves pass from deep to shallow water the velocity of wave is lesser and the wavelength is shorter or vice-versa. When waves are incident to the boundary with an angle, the direction of the waves changes. Such a change in direction is called refraction. It can be noticed that in refraction, the wavelength and velocity change but frequency remains the same. **Diffraction** Figure 7.16 Refraction of plane wave Diffraction is the spreading of waves from the straight-on direction through a gap (or) moves around an obstacle. The wave that passes the edges of the gap of the obstacle spread out. Figure 7.17 and 7.18 show water waves in ripple tank spreading out after they pass through the gap. In Figure 7.17 the wider the gap, the less the waves spread out. In Figure 7.18 the narrower the gap, the more the waves spread out. Note that the wavelength does not change after diffraction. most of the waves have changed direction They have been diffracted Figure 7.18 Diffraction of water waves through narrow gap Diffraction around an obstacle includes radio waves that are diffracted as they pass over the hill. (Figure 7.19) **Reviewed Exercise** 1\. What causes refraction of water waves? 2\. Does the speed of water waves depend upon the depth of water?